1. Field of the Invention
This invention relates generally to copolyester melt adhesives, and more specifically, this invention relates to particular copolyester melt adhesives containing benzoic acid esters as modifiers for improving flow characteristics.
2. Description of Prior Art
U.S. Pat. No. 3,669,921, incorporated herein by reference, relates to copolyester melt adhesives derived from terephthalic acid, adipic acid, ethylene glycol and 1,4-butane-diol, or derivatives of these components. These melt adhesives are especially useful in the bonding of fabrics for upholstered items, glass, wood, rubber, plastic sheeting, metal, etc., either to themselves or to other materials. These copolyester melt adhesives are effective in resisting extended contact with dry cleaning and other solvents, and permit increased production rates in various applications. The use of specific amounts of either titanium dioxide or sodium stearate in these copolyesters was found to prevent loss of bond strength due to ageing, and therefore extended the life of the adhesive. This patent states that dyes or dye-receptive agents, color stabilizers, and various other adjuvants may be added to the copolyester adhesives to meet certain specific use requirements. No mention is made of the use of benzoic acid esters as modifiers for improving flow characteristics.
Benzoic acid esters are known for use in polymers. U.S. Pat. No. 3,186,961 discloses the use of various aryl carboxylic acid esters, for example, diethylene glycol dibenzoate, triethylene glycol dibenzoate, etc., in aromatic polyesters of carbonic acid. U.S. Pat. No. 2,044,612 discloses the use of certain benzoates as plasticizers for plastics, including condensation products of polyhydric alcohols and polybasic acids. Canadian Pat. No. 919,190 and British Pat. No. 815,991 also disclose the use of benzoic acid esters as plasticizers for vinyl resins. These patents, however, do not suggest the use of the particular benzoates specified herein for use as modifiers of the particular polyester melt adhesive claimed.